1. Field of the Invention
The present invention relates to an input device which detects a three-dimensional position of an object as an input position.
2. Description of the Related Art
A user of an information processing apparatus usually uses an input interface such as a keyboard, a numeric keypad, and a mouse. As a kind of input interface, a pointing device is known as a means to move a pointer on a display. A mouse is a typical pointing device, but its size and weight are unsuitable for a portable information processing apparatus (e.g., a cellphone, personal digital assistant [PDA], or mobile computer). A touch panel is known as a more portable pointing device. In a touch panel, a user can select or operate graphical user interface elements (icon, button, menu, check box, etc.) by touching a finger or other objects such as a stylus in a desired area of a display.
Jpn. Pat. Appln. KOKAI Publication Nos. 2005-529395 and 2007-531146 disclose a three-dimensional input method of detecting a three-dimensional position of an object with reference to a display.
Jpn. Pat. Appin. KOKAI Publication No. 2005-529395 discloses a computer navigation, which estimates a three-dimensional position of an object with reference to a display, based on the area and ellipse eccentricity of conical infrared rays emitted from a distal end of an object to a display.
Jpn. Pat. Appln. KOKAI Publication No. 2007-531146 discloses a control unit, which detects an electromagnetic beam emitted from a distal end of an object to a display by detectors provided at least one side of the display. The electromagnetic beam is attenuated before reaching the detectors from a position colliding against the display. The control unit of Jpn. Pat. Appln. KOKAI Publication No. 2007-531146 estimates the distance and angle (three-dimensional position) of the object with reference to the display, based on the intensity of electromagnetic beam detected by the detectors.
According to the computer navigation of Jpn. Pat. Appln. KOKAI Publication No. 2005-529395 and the control unit of Jpn. Pat. Appln. KOKAI Publication No. 2007-531146, even when an object does not touch a display, a three-dimensional position of the object can be detected with reference to the display.
There is another known three-dimensional input device, which is provided with light-emitting units such as infrared light-emitting diodes (LED) and light-receiving units such as photodiodes, around a display. Specifically, there are two known methods of detecting a three-dimensional position. One method (reflection method) detects a three-dimensional position based on changes in the intensity of received light caused by that an object reflects light emitted from a light-emitting unit (hereinafter, simply called an inspection light). The other method (transmission method) detects a three-dimensional position based on changes in the intensity of received light caused by that an object blocks light emitted from a light-emitting unit.
Jpn. Pat. Appln. KOKAI Publication No. 2004-297601 discloses a method of saving electrical energy in a mobile terminal. A mobile terminal disclosed in the Jpn. Pat. Appln. KOKAI Publication No. 2004-297601 consists of a first unit provided with an input device such as a key panel having a lighting function, and a second unit to expose and cover the input device by sliding over the first unit. In the above mobile terminal, the input device is lit while being exposed by the second unit, and not lit while being covered by the second unit. Therefore, according to the Jpn. Pat. Appln. KOKAI Publication No. 2004-297601, a so-called slide-type mobile terminal efficiently turns on an input device, and reduces energy consumption.
In the above reflection- and transmission-type three-dimensional input devices, the light-emitting unit and light-receiving unit must be closely arranged, and operated to provide high detection accuracy. In other words, greater electrical power is required to obtain higher detection accuracy. If the light-emitting and light-receiving units are operated while a valid input is not obtained, electrical energy is wasted. Especially, in a battery-operated portable information processing apparatus, the energy consumption of an input unit reduces the operable time of the apparatus. The three-dimensional input device is not necessarily used in a slide-type mobile terminal, and the energy-saving method of the Jpn. Pat. Appln. KOKAI Publication No. 2004-297601 is not necessarily used.